1. Field of the Invention
The invention relates to a print control apparatus, a print control method, and a memory medium. More particularly, the invention relates to a print control apparatus for controlling the operation of a printer having a plurality of dedicated printer engines for a plurality of colors, dividing print data described by a page description language into a plurality of bands page by page, converting the print data of each band to a display list, and further developing the display list to bit map data. The invention also relates to a print control method which is applied to such a print control apparatus and a memory medium in which a program for executing such a print control method has been stored.
2. Related Background Art
Hitherto, with respect to a printer for dividing print data of one page into a plurality of bands and performing a bit map developing process every band, particularly, a printer of a tandem system having a dedicated printer engine for each of yellow, magenta, cyan, and black.
FIG. 2 is a block diagram showing a schematic construction of a conventional printer apparatus such as a tandem system color printer or the like.
In FIG. 2, reference numeral 17 denotes a host computer having a printer driver 18 for controlling a printer 11. Reference numeral 11 denotes the printer of the tandem system and has a controller 12 and printer engines 13, 14, 15, and 16. The printer engines 13, 14, 15, and 16 execute printing in yellow (Y), magenta (M), cyan (C), and black (K).
Print data formed by the printer driver 18 of the host computer is transmitted to the printer 11 through a communication medium 19 such as a network or the like and printed.
In such a conventional printer, print data of one page which is received from the host computer is developed to bit map data and, when the formation of the bit map data of one page per color is finished, an image is formed onto a recording medium in each printer engine.
In a conventional printer of a system other than the tandem system, mainly for the purpose of saving a memory and improving a printing speed, print data of one page which is received from the host computer 17 is divided into a plurality of bands, a display list is formed every band, and upon printing, the development of the display list to the bit map data and a shipping of the bit map data (data transfer to a printer engine) are simultaneously performed.
Since the printer cannot stop a paper conveyance during the operation, the shipping has to be continuously performed with respect to the data of one page. Therefore, until the end of shipping of a certain band, the bit map data of the next band has to be prepared. When the shipping of the certain band is finished, if the bit map data of the next band is not prepared, a correct print result cannot be obtained. This state is called xe2x80x9coverrunxe2x80x9d. Now, for example, assuming that a printing speed of the printer engine is equal to 16 pages/min, it is necessary to form bit map data of one page within 3.75 seconds. In case of dividing one page into three bands and processing them, bit map data of one band has to be formed within 1.25 seconds. If the time exceeds this time, an overrun occurs.
If it is determined that the overrun occurs as a result of prediction based on a development prediction time regarding a certain band, a display list is previously developed to bit map data and stored for such a band before the printing is started. Thus, since the development of the band to the bit map data is not performed at the time of shipping of the bit map data, the overrun can be prevented.
In case of the system instead of the tandem system, since it is sufficient to sequentially form images onto a transfer material or an intermediate transfer material in the order of YMCK every color, a controller similar to a monochromatic printer can be used.
In the printer of the tandem system, however, in order to further realize a high speed, since it is necessary to simultaneously form an image of the same page by printer engines of a plurality of colors or form images of different pages onto a recording medium, bit map data of each color is previously developed in a page memory as mentioned above and, after that, the printing process is started.
In the conventional printer of the tandem system as mentioned above, after completion of the development of the bit map data of one page, the paper feed is performed and the printing process is performed. Therefore, although the recording time according to the tandem system can be reduced, there is a problem that it takes time for the developing process and it is difficult to improve the performance. Therefore, a method whereby a printing system for performing a band process is used for the printer of the tandem system is considered.
To perform the band process in the printer of the tandem system, it is necessary to simultaneously form images of the bands of the respective colors. Therefore, when it takes long time for development of a certain color, even if there is a surplus time for the developing processes of the other colors, an overrun occurs. There is, consequently, a problem that only a print result of a reduced resolution can be obtained.
For the developing process, a hard renderer of each color simultaneously issues an access request to the display list, an arbitrator for arbitrating the access requests is necessary.
FIG. 4 is a block diagram showing an example of an arbitrator which is necessary when the band process is applied to the printer of the tandem system.
In FIG. 4, reference numeral 51 denotes an access request selector for selecting one of access request signals (REQ-Y, REQ-M, REQ-C, REQ-K) of Y, M, C, and K components; 52 an address selector for selecting one of request destination addresses (ADDRESS-Y, ADDRESS-M, ADDRESS-C, ADDRESS-K) corresponding to the access request signal selected by the access request selector 51; and 53 a data transmitter for returning data (DATA) from a request destination regarding the access request signal selected by the access request selector 51 to a requesting source and forming a signal (DTE: Data Enable) showing the validity of the data. A priority has been set to the access request selector 51 for each access request signal. The access request selector 51 selects the access request signal in accordance with this priority.
However, if the band process is simply realized by the printer of the tandem system, there is a problem that in the hard renderer corresponding to the access request signal of a low priority, there is a possibility that the overrun occurs even in the band in which it is presumed that no overrun would occur on the basis of a development prediction time.
That is, since the access priority has fixedly been determined in the conventional access request selector 51, when access factors compete (when interruption processing request have simultaneously been generated), the process of the hard renderer of a low priority is made to wait irrespective of the development prediction time. This is because, however, if the hard renderer of a low priority takes the longest time for development of bit map data, a continuation time during which this hard renderer is concerned with the development becomes longer than the prediction time due to the waiting, so that there is a possibility of the occurrence of the overrun which ought not to have occurred according to the prediction.
Although it is also possible to allow a calculating equation of the prediction time to have a sufficient margin so as not to cause the overrun, if such a method is used, the number of bands in which it is determined that the overrun will occur increases, the number of bands which are previously developed to the bit map data increases, resulting in deterioration of the performance.
Although it is also possible that a dedicated display list is formed in each of the hard renderer of each color and stored into each dedicated RAM so as not to compete the access requests, there is a problem that such a method is improper from a viewpoint of saving the memory.
The invention is made in consideration of the above problems and it is an object of the invention to provide a print control apparatus, a print control method, and a memory medium, which can prevent the occurrence of an overrun in a printer having a plurality of printer engines for color printing.
To accomplish the above object, according to the invention, there is provided a print control apparatus for forming bit map data to be outputted to a plurality of printer engines corresponding to a plurality of colors, comprising: analyzing means for dividing print data described by a page description language into a plurality of bands and forming a display list of an intermediate data format into a memory every band; development time calculating means for calculating a development prediction time which is required when developing into the bit map data on the basis of the display list every band and every color; a plurality of developing means each for developing into the bit map data band by band on the basis of the display list; and arbitrating means for, in the case where access requests to the memory in which the display lists have been stored are issued from at least two of the plurality of developing means, arbitrating the access requests in accordance with priorities for the access requests to the memory which are determined on the basis of the development prediction time calculated by the development time calculating means.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.